1. Field of Invention
This invention relates to controlled release compositions, encapsulation compositions and methods for making and using them.
2. Description of Related Art
There are many microencapsulated delivery systems disclosed in the art to control the release of the encapsulated active, or provide release when a specific trigger is applied. Such systems have previously suffered from a number of drawbacks.
Core/shell microcapsules that provide release of active upon application of shear or friction are generally not environmentally biodegradable. Such capsules are made using reactive monomers that are not Generally Regarded As Safe (GRAS), and are generally unsafe for direct contact with skin or mucosa membranes. Such microcapsules are made via chemical processes that generally require long batch cycle times.
Polymers that are used to develop a membrane around the active material need to be crosslinked to provide a sufficient barrier to retain the encapsulated active until its desired release. The crosslinking increases the lifetime of these polymers in the environment because the functional groups that breakdown the polymer via microbes are the same functional groups that are used to produce a crosslinked material.
Biodegradable polymers, such as polysaccharides, are utilized to encapsulate volatile actives. However, these systems prematurely release the encapsulated active, especially in any formulation that contains water.
When polysaccharide-based microcapsules are incorporated into anhydrous product forms, these materials will release the active as soon as they come in contact with water, or prematurely release the encapsulated payload in the supply chain due to humidity/temperature effects. Often, it is desired to retain the active even after exposure to water. For example, it is desired to have a microcapsule survive the dilute environment in a washing machine, deposit onto the laundered fabrics, retain fragrance within the microcapsule during high temperature drying, and subsequently release the fragrance over a long duration of time from the fabric. It may be desired to have bursts of fragrance from an antiperspirant or deodorant product even in the absence of perspiration. It may be desired to retain flavor during the baking process, and release the flavor when the baked item is chewed. It may be desired to incorporate flavor particles directly into the dough when making snack foods (such as potato chips), rather than sprinkling on the flavors after the chip is fried. Such an approach can eliminate the mess associated with consuming flavored chips. It may be desired to incorporate flavor particles into a chewing gum to deliver a burst of a flavor upon chewing.
In order to deliver a consumer noticeable benefit, yet deliver that benefit at a low cost, encapsulation is used to isolate a uniquely different fragrance or flavor active from the non-encapsulated fragrance or flavor that is incorporated into the formulation. Acclamation to a flavor or fragrance requires a much higher concentration of the same fragrance or flavor to achieve noticeability. The invention allows one to encapsulate a uniquely different fragrance or flavor to incorporate into the composition, and achieve noticeability at significantly lower concentrations of the encapsulated active.
Friable capsules that are disclosed in the art are specifically core/shell capsules. “Matrix” type of morphology wherein small droplets of the active material are surrounded by shell material are exclusively found in the area of water triggered release technologies (flavors, fragrances, vitamins, silicone oils, etc.). Matrix particles are generally not designed to provide friction-triggered release.
In order to incorporate friable microcapsules into anhydrous products (for example antiperspirant/deodorants, dry laundry powder, baking goods), it is necessary to remove the water from slurries of core/shell microcapsule. Spray drying is a well-known, commercially viable, and inexpensive way to achieve a dry powder. Spray drying of water insoluble, friable microcapsules must be done with utmost care to minimize fracture of the microcapsules during the spray drying process. Generally, only small particle size particles can be dried effectively without fracturing. The high fracture strength of these small particles reduces the performance benefit (i.e. normal consumer activities would not generate enough friction or stress to fracture a sufficient number of these microcapsules). Larger dry particles are preferred since they are easier to fracture, and they can deliver a greater volume of encapsulated material when fractured. However, such large core/shell particles will fracture during the spray drying process.
Hence, it is difficult to achieve a free flowing powder, water insoluble or water swellable, environmentally biodegradable, matrix microcapsule particle that provides a non-water triggered release profile. It is even more difficult to achieve an affordable microcapsule in a dehydrated powder form without incurring significant loss of the encapsulated active during the dehydration process. It is even more difficult to achieve a microcapsule that retains the encapsulated actives even under highly dilute aqueous conditions.
All references cited herein are incorporated herein by reference in their entireties. The citation of any reference is not to be construed as an admission that it is prior art with respect to the present invention. To the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.